The 31-year-old royal has been belting out his favourite hits 'Yellow' and 'Paradise' in the hope the little one, who was born last week, will go back to sleep as he is up six times a night and is keeping Carole and Michael Middleton, the parents of Duchess Catherine - previously known as Kate Middleton - awake.
A royal insider said: ''William had no idea it would be this tough.
''He's using a bizarre tactic of belting out Coldplay anthems at all hours of the night even though he can barely hold a note.
''It's even keeping Kate's parents awake. His favourite song is 'Paradise' and he also loves doing 'Yellow'.
''Coldplay aren't even his favourite band, but George responds to their songs the most and settles back down.''
William and Catherine are looking after George at her parents' £4.7 million home in Bucklebury, Berkshire, south east England, but William has been ducking out of morning greetings by heading back to bed to catch up with some much-needed sleep following his nighttime singing sessions.
The insider added to the Daily Star newspaper: ''Wills is shattered by the morning so he heads to bed for a couple of hours and Kate springs back into action along with her parents.''
There are currently five separate teams working on 'Game of Thrones' projects at HBO.
She's a big fan of the band and this week she got to perform with them.